cfimport.py

import sys
import threading


NLOOPS = 10
NTHREADS = 30


def t1():
    from concurrent.futures import ThreadPoolExecutor

def t2():
    from concurrent.futures.thread import ThreadPoolExecutor


def main():
    for j in range(NLOOPS):
        threads = []
        for i in range(NTHREADS):
            threads.append(threading.Thread(target=t2 if i % 1 else t1))
        for thread in threads:
            thread.start()
        for thread in threads:
            thread.join()
        sys.modules.pop('concurrent.futures', None)
        sys.modules.pop('concurrent.futures.thread', None)


main()